Months of speculation, negotiations and deliberation bore fruit in the early hours of Tuesday morning as the open secret of the 23-year-old's United return was made official.

Four years on from departing Old Trafford without making a first-team start, Pogba signed a five-year contract with the option of a sixth season after United agreed to pay an eye-watering 105million euros (£89million).

Juventus revealed the deal could increase by a further five million euros (£4.25million) depending on targets being met at a club the midfielder plumped for ahead of Champions League holders Real Madrid.

Press Association Sport understands the Spanish giants were pushing to sign Pogba until the death, becoming more focused on snaring the midfielder as a return to Old Trafford edged closer.

However, re-joining the club he left in 2012 proved more alluring - even though United are readying themselves for Europa League action - given Pogba's desire to get to the top individually and collectively.

"I want to win the league for the first time with United, because I hadn't won the league when I left," he told MUTV.

"The Champions League of course. And, personally, one of my dreams is to win the Ballon d'Or.

"That will come with time, hopefully, but first I want to win the Premier League, which I have never done."

Pogba won four Serie A titles during his time at Juventus, with United tracking his improvements closely ever since his departure as an interest in bringing him back to Old Trafford grew.

The move has been a number of years in the making and may have happened sooner had it not, in part, been due to manager-related issues.

The process of signing Pogba began two months ago but has proved very complicated, given the image rights, tax matters and contract specifics stipulated by Mino Raiola, whose own fee also needed to be covered.

Executive vice-chairman Ed Woodward has had a good working relationship with the agent for the past three years, although it required several meetings and numerous hours with him and lawyer Rafaela Pimenta to sort Pogba's playing and image right contracts.

It is, in fact, considered among the top three most complicated player deals at the club, although Woodward's experience in the 1990s as a tax advisor is said to have helped deal with such difficulties.

Juventus are believed to have had to contend with more complications and, aside from bickering over the fee, negotiations were amicable, with the club having just two face-to-face meetings towards the move's completion.

Getting the deal over the line is understood to have delighted those at United as much as their fans, given they have not only accrued a fine talent but shown they can again take on the might of Madrid and Barcelona in the transfer market.

Turning down the Bernabeu in favour of Old Trafford certainly appears a big deal, with the allure of working with Mourinho one of the key attractions.

Since his appointment the Portuguese has been keen to sign Pogba - a player who left Old Trafford without burning bridges and is now looking to justify his lofty price tag.

"He's a very young player, an unbelievable midfield player with such physicality but, at the same time, such agility, co-ordination, skill," Mourinho said. "He has everything.

"What he has to learn now is how to play with us because I always say that in football you can be a super player, like he is, but a team is a team and you need to learn how to play in the team, and the team needs to learn how to play with you.

"We need to get the best out of him and this will be a process. So if he needs protection, I am here to protect.

"I know some people think that he arrives here now and, the first time he touches the ball, he scores, but I'm here to protect him and give him the best conditions to be what we think he is going to be, which is a football player for Man United, a reference for this club. I'm so happy."